Russia's Foreign Ministry had taken "emergency measures to clarify circumstances of incident with Russian jet flying over Syria," according to Interfax.

Meanwhile Russian news reports say the Syrian Aviation Authority has released a message denying the reports:

“We contacted the service that monitors traffic within Syrian airspace. None of the air traffic control services or other ground services at the airports in Damascus and Latakia have confirmed the information of a Russian plane plane being fired at."

The reports conflict with the known capabilities of rebel groups in Syria, according to Syrian arms expert Eliot Higgins:

@brian_whit @leshaque And I very much doubt the opposition are capable of launching and targeting larger missiles